Watertube and method of making and assembling same within a boiler or heat exchanger

ABSTRACT

A one-piece tube for use as a watertube within a watertube boiler or heat exchanger has a free end section that is formed to have an integral, outward-extending circumferential ring, or flange, a spaced distance from an adjacent end face of the tube. A boiler is provided that has an elongate header and a plurality of separate watertubes each having an intermediate section and opposite end sections. An end section of each watertube is connected to the header. The intermediate section of each watertube has a substantially constant outer diameter along its full length and is closely spaced to adjacent watertubes within the combustion chamber. At least one of the end sections of each watertube has a transition that reduces the diameter of the watertube as it extends from the intermediate section to an outwardly-extending circumferential flange. This arrangement permits close spacing of the connection sites of the watertubes to the header and permits the connection sites to be provided in a linear array.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a continuation-in-part application of U.S. Utility application No. Ser. 11/380,456, filed Apr. 27, 2006, and entitled “Watertube and Method of Making and Assembling same within a Boiler or Heat Exchanger.”

FIELD OF THE INVENTION

The present invention relates to a boiler and/or heat exchanger used in a domestic and/or commercial heating and/or hot water and/or steam system, and more specifically, the present invention relates to a watertube structure and to methods of making a watertube and assembling it within a boiler and/or similar heat exchanger. The invention also relates to a watertube, a header and watertube assembly, a boiler having the header and watertube assembly, and a method of assembling the boiler.

BACKGROUND OF THE INVENTION

Examples of boilers having watertubes are provided by U.S. Pat. No. 1,824,256 issued to Bryan and U.S. Pat. No. 4,993,368 issued to Jones et al. For example, the Bryan patent discloses a boiler having a plurality of bent watertubes extending through a combustion chamber. The ends of the bent watertubes connect to the upper and lower domes of the boiler via separately manufactured tapered fittings.

A return pipe of the heating system is connected to the base header for returning cool water or like fluid to the boiler. The cool water or like fluid flows upward into the plurality of closely-spaced watertubes where the water or like fluid is heated as it passes through and/or adjacent the combustion chamber. A delivery pipe connects to the top of the dome header which receives the heater water, like fluid, or steam from the watertubes and delivers the steam and/or heated water or fluid to the system via the delivery pipe.

Typically, such a boiler will have a front and a rear with the headers extending horizontally in a front-to-rear direction at the top and bottom of the boiler. A plurality of closely-spaced watertubes typically having undulating intermediate sections extends through the combustion chamber. The upper end sections of the watertubes connect to the dome header, and lower end sections connect to the base header. Each watertube essentially extends through the boiler within a vertically-disposed plane that is parallel with the front and rear of the boiler and that is parallel to all other planes defined by the other watertubes.

Each manifold, dome, header, or like casting is typically provided in the form of an elongate hollow pipe or the like that has a relatively large diameter as compared to the diameter of the watertubes. Conventionally, the end sections of the watertubes connect to the manifolds, headers, domes, or castings via separately manufactured nipple fasteners or end fittings.

A conventional watertube for a boiler and/or heat exchanger is typically made of a metallic material and has substantially constant inner and outer diameters from end-to-end. The intermediate sections of the tubes extend in various bent, serpentine, or other shapes or patterns between opposite free ends. A separately-manufactured tapered fitting is typically welded to each free end to enable the tubes to be connected in a fluid-tight and secure manner to domes, manifolds, headers and/or like castings.

The separately-manufactured fitting typically provides the end of the tube with an outwardly-extending circumferential ring and a tapered end section. The tapered end section is inserted into a corresponding tapered hole, port or socket in a dome, manifold, headeror like casting. A clip, clasp or like fastener is typically applied to the circumferential ring to ensure that the inserted tube end remains in engagement with the dome, manifold, header or like casting.

A 45 degree angle fillet weld is typically used to connect the fitting to the tube. The 45 degree angle fillet weld extends from an upper, exposed, radially-extending end surface of the circumferential ring to the adjacent outer wall surface of the tube. A problem with the use of the fillet weld is that the fillet weld eliminates any clean or flat surface of the circumferential flange on which a force can be readily applied to drive the tube end into the hole in a dome or the like. Existence of the fillet weld further complicates the already difficult and inefficient process of handling relatively heavy tubes within small spaces available during a boiler or heat exchanger assembly and the process of driving the tube ends into position within the boiler in a manner that provides leak-free connections.

Accordingly, there is a need for a watertube structure that can be handled and driven more easily into a hole, port or socket of a dome, manifold, or casting to create a leak-free connection therewith. In addition, there is a need for an efficient process of assembling watertubes in boilers and heat exchangers and for making watertubes.

The conventional watertube is made of steel, has constant inner and outer diameters from end-to-end, and weighs at least about fifty pounds. The intermediate sections extend in various bent, serpentine, or other shapes as they extend within the combustion chamber of boiler. The separately-manufactured fittings are typically welded to each free end to enable the ends of the watertubes to be connected in a fluid-tight and secure manner to water domes, manifolds, headers and like castings as discussed above.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, a watertube for use to conduct water or steam is provided. The watertube has an intermediate portion with a first end portion and a second end portion. The first end portion has an integrally formed radially outward extending, circumferential flange which is spaced from a free end of the first end portion. The flange is formed to accept a driving force applied in a direction parallel to the longitudinal axis of the first end portion toward the free end of the first end portion without failing. A radially extending surface on a distal side of the flange is provided. The radially extending surface is dimensioned to engage an apparatus which exerts the driving force thereon. The first end portion has a tapered outer wall which tapers down from the flange to the free end of the first end portion. The application of an axial force to the radially extending surface of the flange results in the tapered first end portion being received in an opening of a manifold and secured in fluid-tight engagement therein.

According to another aspect of the present invention, a method of making a tube for a boiler or heat exchanger is provided. A one-piece tube for use as a watertube within a boiler or heat exchanger has a free end section of a predetermined substantially-constant diameter. The method includes the step of forming an integral, outward-extending circumferential ring, or flange, on the free end section of the tube a spaced distance from an adjacent end face of the tube. This may be accomplished by radially expanding the tube within the free end section followed by axially compressing the free end section to cause a portion of the tube to bulge radially outward to form the circumferential ring or flange. The method can also include the step of forming the free end section of the tube that extends from the circumferential ring, or flange, to the adjacent end face of the tube with a taper such that the diameter of an outer wall of the tube progressively decreases from the circumferential ring, or flange, to the end face. Preferably, the tube is made of a metallic material and the forming process is cold or hot forming process.

According to yet another aspect of the present invention, a method of assembling a watertube boiler or heat exchanger is provided. A one-piece metallic tube having a free end section of a predetermined substantially-constant diameter is cold and/or hot-formed to produce an integral circumferential flange extending outwardly from the tube a spaced distance from an adjacent end face of the tube. A force is applied on a radially-extending surface of the circumferential flange to drive the end of the metallic tube into a hole, port or socket of a dome, manifold or like casting of a watertube boiler or heat exchanger to secure the one-piece tube to the dome, manifold, header or like casting. Before being engaged with the dome, manifold, header or like casting, the free end section of the metallic tube that extends from the circumferential flange to the adjacent end face can be formed with a taper such that the diameter of an outer wall of the tube progressively decreases from the circumferential flange to the end face.

According to yet another aspect of the present invention, a boiler or heat exchanger is provided. The boiler or heat exchanger has at least a pair of opposed domes, manifolds, or like castings and one or more metallic watertubes each having opposite ends connected to the opposed domes, manifolds, or like castings. At least one end section of the one-piece watertube is formed to have an integral outwardly-extending circumferential flange. The flange provides a readily-engagable, radially-extending surface on which a substantially axially-directed force can be applied to drive the end of the tube into sealing engagement with a hole, port, or socket of one of the domes, manifolds, or like castings. Preferably, a portion of the tube extending from the circumferential flange to an adjacent end face of the tube is formed with an inward taper such that a diameter of an outer wall of the tube progressively decreases from the circumferential flange to the end face. A wall defining the hole, port, or socket in the dome, manifold or like casting can be tapered to enable tight engagement with the tapered end of the tube. The watertube can have a substantially serpentine shape between its opposite ends.

According to yet another aspect of the present invention, a boiler is provided that has an elongate base header located adjacent a base of the boiler, an elongate dome header located at the top of the boiler, and a plurality of separate watertubes each having an intermediate section and opposite end sections. An upper one of the end sections of each watertube is connected to the dome header and a lower one of the end sections of each watertube is connected to the base header such that the intermediate section extends through a combustion chamber of the boiler. The intermediate section of each watertube has a substantially constant outer diameter along its full length and is closely spaced to adjacent watertubes within the combustion chamber. At least one of the end sections of each watertube has a transition that reduces the diameter of the watertube as it extends from the intermediate section and transitions to a reduced-diameter free end tip of the end section.

According to some embodiments, the above-referenced end section of the watertube has an outwardly-extending circumferential flange. The flange is located on an opposite side of the transition from the intermediate section of the watertube such that the flange extends from a reduced-diameter part of the end section adjacent the free end tip. The outwardly-extending circumferential flange has a peripheral outer edge of a predetermined diameter that closely matches or is not significantly greater than the constant outer diameter of the intermediate section. Further, the base header and the dome header have a series of sockets for receiving the tip portion of the end sections of the watertubes, and preferably the series of sockets of at least one of the base header and dome header is provided as a closely-spaced linear (non-staggered) array of sockets.

According to yet another aspect of the present invention, a watertube and header assembly for a boiler or heat exchanger is provided and includes an elongate, hollow header extending within the boiler or heat exchanger and a plurality of separate, closely-spaced, elongate watertubes extending from the header. Each of the watertubes has an intermediate section and at least one end section. The end section is the part of the watertube that connects to the header, and the intermediate section has a substantially constant outer diameter along its full length and is closely spaced to adjacent intermediate sections of like watertubes. The end section of each watertube has a transition that reduces the diameter of the watertube as it extends from the intermediate section to an outward-extending circumferential flange located on an opposite side of the transition relative to the intermediate section. Thus, the flange extends from a part of the end section having a reduced diameter. Preferably, the outward-extending circumferential flange has a peripheral outer edge of a predetermined diameter that closely matches the outer diameter of said intermediate section, and the header has a series of sockets for receiving the free end tip portions of the end sections of the watertubes. The series of sockets are provided as a closely-spaced linear array of sockets along a length of the header.

According to yet another aspect of the present invention, a watertube for a boiler or heat exchanger is provided and comprises an elongate tube having an intermediate section and opposite end sections. The intermediate section has a substantially constant outer diameter along its full length and bends providing the intermediate section with a serpentine-like shape. Each of the end sections has a transition that reduces the diameter of the watertube as it extends from the intermediate section to an outwardly-extending circumferential flange located on an opposite side of the transition relative to the intermediate section. Thus, the flange extends from a reduced-diameter part of the end section. The outwardly-extending circumferential flange has a peripheral outer edge of a predetermined diameter that closely matches the outer diameter of the intermediate section.

According to a final aspect of the present invention, a method of assembling a boiler is provided. The method includes the steps of mounting an elongate hollow base header below a combustion chamber of the boiler, mounting an elongate hollow dome header above the combustion chamber of the boiler, and providing only a linear array of sockets in each of the base and dome headers. A plurality of watertubes is provided such that each of the watertubes includes an intermediate section of substantially constant outer diameter and opposite end sections. Each of the end sections has a transition that reduces the outer diameter of the watertube as it extends from the intermediate section to an outwardly-extending circumferential flange located on an opposite side of the transition relative to the intermediate section. Each outward-extending circumferential flange has a peripheral outer edge of a predetermined diameter that closely matches the outer diameter of the intermediate section. The method further includes the step of connecting the plurality of water tubes to the linear array of sockets of the base and dome headers such that the intermediate sections of the watertubes extend through the combustion chamber of the boiler closely-spaced to intermediate sections of the adjacent watertubes.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention should become apparent from the following description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a watertube boiler according to the above referenced prior art Bryan patent;

FIG. 2 is a view illustrating the staggered connection pattern of prior art watertubes to a header;

FIG. 3 is a schematic view of a tube expansion method step according to the present invention;

FIG. 4 is a cross-sectional view taken along line 3-3 of FIG. 3;

FIG. 5 is a schematic view of a ring, or flange, forming step according to the present invention;

FIG. 6 is a cross-sectional view taken along line 5-5 of FIG. 5;

FIG. 7 is a schematic view of a taper forming step according to the present invention;

FIG. 8 is a cross-sectional view taken along line 7-7 of FIG. 7;

FIG. 9 is a perspective view of an end section of a formed watertube according to the present invention;

FIG. 10 is a cross-sectional view taken along line 9-9 of FIG. 9:

FIG. 11 is a front view of a watertube according to the present invention;

FIG. 12 is a side view of the watertube of FIG. 11;

FIG. 13 is an enlarged view of an end section of the watertube of FIG. 11;

FIG. 14 is a perspective view of a watertube and header assembly according to the present invention;

FIG. 15 is a cross-sectional view taken along line 8-8 of FIG. 14;

FIG. 16 is a cross-sectional view of the watertube of FIG. 11 assembled to a header according to the present invention; and

FIG. 17 is a front elevation view of an assembly of the watertube of FIG. 11 connected to upper and lower headers.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to watertubes that are used in commercial boilers, heat exchangers, and like apparatus. FIG. 1 illustrates an example of a watertube boiler 10 that is known in the art. The boiler 10 includes at least one upper dome 12 and at least one base header 16. The so-called bent watertubes 20 have opposite ends interconnecting the base header 16 to the dome 12. A serpentine portion of each watertube 20 extends within a combustion chamber 22 of the boiler. System water is fed into the boiler 10 or dome 12 and travels within the watertubes 20. The water is heated in the watertubes 20 and the heated water or steam flows from the watertubes 20 into the dome 12 and then to a system supply pipe.

A typical watertube is made of a metallic material. The inner and outer diameters of such a watertube are typically constant from end-to-end. For example, the outer diameter of each tube may be 1.5 inch, and the inner diameter of each tube may be 1.25 inch thereby providing a tube wall thickness of about 0.125 inch. The watertubes can extend in serpentine or other shaped paths including linear shaped paths. The watertubes are assembled within boilers, heat exchangers and like apparatus.

A watertube 30 according to the present invention is similar to watertube 20 discussed above; however, the watertube 30 is provided as one-piece without the use of separately-manufactured fittings, nipples, or like coupling devices secured or welded thereto. Rather, the watertube 30 according to the present invention has a free end section that is formed into a desired shape without any component being added or welded thereto. Accordingly, there are no fillet welds or the like capable of providing leakage paths.

The method of making the watertube 30 is shown in FIGS. 3-8. A tube 30 a is initially provided having an end section 32 with a uniform and constant inner diameter and a uniform and constant outer diameter. A holding clamp 34 is positioned about a portion of the tube to grip the tube a predetermined spaced distance from an adjacent end face 36 of the tube 30 a. The holding clamp 34 rigidly supports the tube relative to one or more dies 38 that are capable of being inserted into the end section 32 to radially expand the end section 32.

The die 38 shown in FIGS. 3 and 4 includes a tip 40 of a diameter sufficiently small to permit insertion within the tube 30 a without resistance. An opposite end of the die 38 includes an expansion section 42 that is larger in diameter than the inner diameter of the tube 30. The die 38 also includes an intermediate frustoconical section 44 that transitions the diameter of the die 38 from that of the tip 40 to that of the expansion section 42. Accordingly, the outer and inner diameters of the tube 30 can be radially expanded by inserting the die 38 therein with a predetermined amount of force, and/or by sequentially inserting a set of dies each having a progressively larger diameter expansion section. Thus, end section 32 can be expanded to a desired inner diameter D1.

After the end section 32 is expanded, an upsetting element 46 or the like engages the end face 36 and applies an axially directed force thereon to thereby compress the axial length of the end section 32. The upsetting element 46 can include an insertable support section (not shown) that extends within the end section 32 of the tube 30 while the upsetting element 46 applies the desired axial force. A face 48 of the holding clamp 34 has an annular recessed molding area 50 into which the end section 32 bulges in response to the axial compression. This results in the formation of an integral, radially outward extending, circumferential ring, or flange, 52. Preferably, the flange 52 includes a radially-extending, substantially-flat surface 54 that is located on a distal side of the flange 52 and that is readily engagable by a forked or like driving tool (not shown) for reasons discussed in greater detail below.

After the end section 32 is radially expanded and axially compressed, one or more dies 56 is utilized to provide the end section 32 with an outer diameter D2 that tapers inward from the flange 52 to the end face 36. For example, the die 56 can have a tapered inner surface 58 that is telescopically forced over the end section 32 to thereby radially contract the outer and inner diameters of the end section 32. In this way, the die 56, or a set of dies, can be used to provide the end section 32 with a frustoconical, or gradually tapered, outer wall 60.

As stated above, the tube 30 can be made of metallic material, for example steel. Of course, watertubes made of other materials can also be used. Preferably, the forming steps are cold and/or hot-forming steps without the use of any stress-relieving process steps, and both ends of the tube 30 can be formed as described above. Accordingly, the watertube 30 is a one-piece tube without separately-manufactured fittings or nipples and without welded connections.

The watertube 30 having a formed end section 32 as shown in FIGS. 9 and 10 can be assembled in a boiler, heat exchanger, or like apparatus. Preferably, the boiler, heat exchanger, or like apparatus has one or more pairs of opposed domes, headers, manifolds, or like castings. These castings preferably have a tapered hole, port or socket for receiving and engaging a tapered end section 32 of the watertube 30. Accordingly, the end section 32 is aligned with the hole, port or socket and a force is applied to drive the watertube into fluid-tight engagement with the dome, manifold or like casting. For examples of boilers, domes, manifolds and the like, the disclosures of U.S. Pat. Nos. 1,824,256 and 4,993,368 are incorporated herein by reference.

A forked tool (not shown) or the like is utilized to engage the unobstructed, radially extending surface 54 of the circumferential flange 52 and exert a substantially axially directed force thereon to efficiently drive the tapered end section 32 into the hole, port, or socket. Thereafter, a clip, clasp or like fastener can be placed over the flange 52 to ensure that it remains engaged with the dome, manifold or like casting.

The above described methods, boiler, heat exchanger and like apparatus provide watertubes that can be driven more efficiently and more easily into domes, manifolds and the like. The use of separate fittings and welds are eliminated thereby eliminating the possibility of weld leaks and the like. In addition, a driving force can be applied to the tube during the assembly process without concern of creating leakage paths. The end forming process also enables better control over tube tolerances with respect to diameters, tapers and the like to further ensure the formation of fluid-tight connections.

Various changes can be made to the above referenced methods and apparatus. For example, the circumferential flange 52 can be continuous or discontinuous, and the flange surface 54 can be of shapes other than substantially-flat. For example, the flange can be formed with a surface having a series of slots, recesses, or the like adapted to engage the head of a driving tool. One or both ends of the tube can have a formed end, and the tube can extend in a bent or linear path. The taper of the end section can be a gradually continuous uniform taper or a non-uniform varying taper. Alternatively, a uniform, non-tapered end section can be utilized.

Referring to FIG. 2 a conventional staggered pattern of watertubes 112 connected to a header 120 is illustrated. As shown in FIG. 2, the circumferential flanges 114 of the separately-manufactured end fittings extend radially outward of the outer diameter “A” of the watertubes 112. Thus, the existence of the flanges 114 requires sufficient spacing between adjacent watertubes. However, since a given number of closely-spaced watertubes are required along a given length of the header, the connections of the watertubes to the header must be staggered or offset. As shown in FIG. 2, a spacing “B” is required between adjacent watertubes 112 to accommodate the circumferential flanges 14, and the staggering of the connection sites permits the walls of the intermediate sections of the watertubes 112 to have a spacing “C” as viewed from the direction represented by arrow 126. A disadvantage of the staggered pattern of connection sites is that it requires the header 120 to be of an increased size or diameter than otherwise would be desired or necessary.

With the above discussion in mind, a watertube 130 according to the present invention is illustrated in FIGS. 11-14. The watertube 130 has an undulating intermediate section 132 that extends through the combustion chamber of a boiler. The outer diameter “D” of the watertube 130 is substantially constant along the full length of the intermediate section 132 and can be equal to the outer diameter “A” of watertube 112. End sections 134 and 136 extend from the opposite ends of the intermediate section 132. Somewhat similar to the circumferential flange 114 and tip 116 of the watertube 112, the watertube 130 of the present invention can also have outwardly-extending circumferential flanges 138 and free end tips 140 which may or may not be tapered.

However, unlike the watertubes 112, the watertube 130 of the present invention is not of a constant diameter between opposite circumferential flanges 138. Rather, each end section, 134 and 136, includes a transition 142 located between the intermediate section 132 and each circumferential flange 138. See FIG. 13. The transition 142 reduces the inner and outer diameters of the watertube 130 as it extends from the intermediate section 132 toward the circumferential flange 138. For example, the outer diameter “E” of the transition 142 adjacent the circumferential flange 138 is less than that of the outer diameter “D” of the transition 142 adjacent the intermediate section 132. The transition 142 can be provided by tapered walls as shown in FIG. 13 or by walls having a stepped configuration.

The circumferential flange 138, as illustrated in FIG. 13, extends from a part of the watertube 130 having the reduced outer diameter of “E,” and its outermost circumferential edge extends to a diameter of “F.” The outer diameter “F” of the circumferential flange 138 closely matches the outer diameter “D” of the intermediate section 132 of the watertube 130. Accordingly, the existence of the outwardly-extending circumferential flanges 138 from the end sections, 134 and 136, provides no limitation with respect to close-spacing of watertubes 130 where they connect to a header. For example, as best illustrated in FIG. 14, the watertubes according to the present invention can be closely-spaced together in a linear pattern where they extend from header 144 despite the presence of the circumferential flanges.

Accordingly, the transition 142 of the watertube 130 adjacent the circumferential flange 138 accommodates the existence of the outwardly-extending circumferential flange 138, thereby eliminating any spacing requirements as a result of the circumferential flange 138. For example, see FIG. 16 Thus, the watertubes 130 can be spaced together as close as desired in any pattern, linear or otherwise. This, in turn, enables the size or diameter of the header 144 to be reduced. For example, the header 120 required by the staggered pattern of FIG. 2 may need to have a diameter of at least about eight inches to accommodate the offset spacing of the connection sites; whereas, for similar-sized watertube diameters, the header 144 in FIGS. 14-17 may require a diameter of only three inches due to the linear connection site pattern. This provides advantages with respect to increasing the velocity of the fluid through the boiler, improving convective heat transfer within the boiler, and reducing costs with respect to making and assembling the boiler.

In the embodiment of the present invention illustrated in FIGS. 11-13 and 16, the end sections 134 and 136 of the watertube 130 are produced as a result of a forming operation applied to the ends of the watertube 130. Thus, the watertube 130 comprises a single piece of tube in which the transition sections 142 and circumferential flanges 138 are formed using appropriate forming dies or the like.

In contrast, FIGS. 14 and 15 illustrate another embodiment of a watertube 150 according to the present invention. These watertubes have separately applied end fittings 152. The end fitting 152 is secured to a free end of the watertube 150, such as by being welded thereto (the existence of the fillet weld is not shown for purposes of ease of illustration). An intermediate section 154 of the watertube 150 can have a constant outer diameter between opposite end sections. However, at end sections of the watertubes 150, where the watertubes 150 are required to connect to manifolds, headers, domes or like castings 144, the watertubes 150 are provided with a transition 156 that tapers inward from the intermediate section 154 to a reduced outer diameter section 158. The end fitting 152 is secured to the reduced outer diameter section 158 and the circumferential flange 160 provided by the end fitting 152 extends outward from the reduced diameter section 158. As discussed above, the transition 156 enables the outer diameter of the circumferential flange 160 to substantially and closely match the outer diameter of the intermediate section 154. Thus, the existence of the circumferential flange 160 does not restrict close spacing of adjacent watertubes 150 regardless of the connection pattern (staggered, linear, or otherwise).

The transitions 142 and 156 of the watertubes 130 and 150 also accommodate the installation of clips, clasps, fasteners or the like 162 that mechanically secure the watertubes 130 and 150 to the headers, manifolds, domes, castings or the like 144. For instance, as illustrated in FIGS. 14-16, threaded shafts 164 extend from the header 144 and permit the placement of washers 166 or the like that overlap with engage the upper surfaces of circumferential flanges 138 and 160 of adjacent watertubes 130 and 150 and secure the watertubes 130 and 150 to the header 144 via placement of a securement nut 168 or the like. Of course, other fastening mechanisms can be used. Thus, the transitions 142 and 156 not only permit close spacing of watertubes 130 and 150 on the header 144, but also accommodate placement of fasteners 162 that prevent undesired withdrawal of the watertubes 130 and 150 from the header 144 during assembly or use.

FIG. 17 provides a simplified example of a boiler 170 having watertubes 130 and headers 144. The headers 144 are illustrated as being in the form of pipes of a given diameter. This diameter can be reduced as desired due to the use of a linear connection pattern of the watertubes to the header; for instance, see the linear pattern of FIG. 14. A combustion chamber 172 is located at an elevation between the headers 144, and the watertubes 130 extend from the base header through the combustion chamber 172 to the upper header.

The watertubes of the present invention can be efficiently and readily driven into water domes, manifolds, headers and the like despite their close spacing. In addition, the end forming process used to form the ends of watertube 130 enables better control over tube tolerances with respect to diameters, tapers and the like to ensure the formation of fluid-tight connections.

Various changes can be made to the above-referenced watertubes, assemblies, and methods of assembly. For example, the circumferential flanges can be continuous or discontinuous, and can be formed with a surface having a series of slots, recesses, or the like adapted to engage the head of a driving tool. Alternatively, the watertubes can be provided with ends not having circumferential flanges. Also one or both ends of the watertube can have a formed end, and the intermediate section of the watertube can extend in a bent or linear path. The taper of the transition can be a gradually continuous uniform taper or a non-uniform varying taper.

Accordingly, the present invention provides a watertube configuration and watertube-to-header assembly that permits close-spacing of adjacent watertubes without the use of staggered connection patterns. Further, the headers or manifolds to which the watertubes of the present invention connect can be provided of smaller diameters or sizes yet still enable a desired number of watertubes to be connected thereto in a closely-spaced manner. The benefits that will be achieved with such an assembly include improving the velocity of the water, steam, or like fluid through the watertube and header assembly, improving convective heat transfer to the water or like fluid, and reducing manufacturing and assembly costs.

While preferred watertubes, assemblies and methods have been described in detail, various modifications, alterations, and changes may be made to the present invention without departing from the spirit and scope of the present invention as defined in the appended claims. 

1. A watertube for use to conduct water or steam, the watertube comprising: an intermediate portion having a first end portion and a second end portion; the first end portion having an integrally formed, radially outward-extending circumferential flange spaced from a free end of the first end portion, the flange formed to accept a driving force applied in a direction parallel to the longitudinal axis of the first end portion toward the free end of the first end portion without failing; a radially extending surface on a distal side of the flange, the radially extending surface being dimensioned to engage an apparatus which exerts the driving force; the first end portion having a tapered outer wall which tapers down from the flange to the free end of the first end portion; whereby an axial force applied to the radially extending surface of the flange results in the tapered first end portion being received in an opening of a manifold and secured in fluid-tight engagement therein.
 2. The watertube as recited in claim 1, wherein the intermediate portion has a serpentine configuration.
 3. The watertube as recited in claim 1, wherein the first end section has been compressed along its axial length to form the flange.
 4. The watertube as recited in claim 1, wherein the tapered outer wall of the first end portion has a frustoconical configuration.
 5. The watertube as recited in claim 1, wherein a fastener is positioned on the flange to ensure that the first end portion of the watertube will be retained in the opening of the manifold.
 6. The watertube as recited in claim 1, wherein the flange is continuous about the circumference of the first end portion of the watertube.
 7. The watertube as recited in claim 1, wherein the tapered outer wall has a non-uniform, varying taper configuration.
 8. The watertube as recited in claim 1, the second end portion comprising: an integrally formed, radially outward-extending, circumferential second flange spaced from a free end of the second end portion, the second flange formed to accept a driving force applied in a direction parallel to the longitudinal axis of the second end portion in a direction toward the free end of the second end portion without failing; a second radially-extending surface on a distal side of the second flange, the second radially-extending surface being dimensioned to engage an apparatus which exerts the driving force; the second end portion having a tapered second outer wall which tapers down from the second flange to the free end of the second end portion; whereby an axial force applied to the second radially-extending surface of the second flange results in the tapered second end portion being received in an opening of a manifold and secured in fluid-tight engagement therein.
 9. A boiler, comprising: an elongate header located adjacent the boiler; a plurality of watertubes each having an intermediate section and an end section, the end section of each of the watertubes connecting to the header; the intermediate section of each of the watertubes having a substantially constant outer diameter; the end section of each of the watertubes having a transition that reduces the diameter of the watertube as it extends from the intermediate section; and the end section of each of the watertubes having an outwardly-extending circumferential flange located on an opposite side of said transition from said intermediate section such that said flange extends from a part of said end section of reduced diameter.
 10. A boiler according to claim 9, wherein the outwardly-extending circumferential flange has a peripheral outer edge of a predetermined diameter that closely matches or is not significantly greater than the outer diameter of the intermediate section.
 11. A boiler according to claim 9, wherein the header has a series of sockets for receiving a portion of the end sections of the watertubes, and wherein the series of sockets of the header is provided solely as a closely-spaced, non-staggered, linear array of sockets.
 12. A boiler according to claim 9, wherein a fastener is secured to the header between each of said sockets and extends over and engages top surfaces of the outwardly-extending circumferential flanges of an adjacent pair of the watertubes to prevent withdrawal of the watertubes from the sockets.
 13. A boiler according to claim 9, wherein each of the watertubes are identical and made of a single length of tube with integral end sections having the transition and outwardly-extending circumferential flange formed by a forming operation.
 14. A boiler according to claim 9, wherein each of the watertubes are identical and include an end fitting welded thereto for providing the outwardly-extending circumferential flange.
 15. A boiler according to claim 9, wherein the watertubes each have a second end section which extends from the intermediate section, the second end section of each of the watertubes including said transition and said outwardly-extending circumferential flange.
 16. A boiler according to claim 9, wherein the intermediate section of each of the watertubes extends in a non-linear, serpentine path.
 17. A watertube and header assembly for a boiler or heat exchanger, comprising: an elongate, hollow header extending within the boiler or heat exchanger; and a plurality of separate, closely-spaced, elongate watertubes extending from the header; each of the watertubes having an intermediate section and at least one end section, the end section of each of the watertubes being connected to the header; the intermediate section of each of the watertubes having a substantially constant outer diameter along its full length and being closely spaced to adjacent watertubes; and the end section of each of the watertubes having a transition that reduces the diameter of the watertube as it extends from the intermediate section.
 18. A watertube and header assembly according to claim 17, wherein an outwardly-extending circumferential flange is located on an opposite side of the transition relative to the intermediate section such that the flange extends from a reduced-diameter part of the end section.
 19. A watertube and header assembly according to claim 18, wherein the outwardly-extending circumferential flange has a peripheral outer edge of a predetermined diameter that closely matches the outer diameter of the intermediate section.
 20. A watertube and boiler assembly according to claim 19, wherein the header has a series of sockets for receiving free end tip portions of the end sections of the watertubes, the series of sockets being provided as a closely-spaced linear array of sockets along a length of the header.
 21. A watertube and boiler according to claim 20, wherein a fastener is secured to the header between each of the sockets and extends over and engages upper surfaces of the outwardly-extending circumferential flanges of an adjacent pair of the watertubes to prevent withdrawal of the free end tip portions of the watertubes from the sockets.
 22. A watertube for a boiler or heat exchanger, comprising an intermediate section and opposite end sections, the intermediate section having a substantially constant outer diameter along its full length and having bends providing the intermediate section with a serpentine-like shape, each of the opposite end sections having a transition that reduces the diameter of the watertube as it extends from the intermediate section to an outwardly-extending circumferential flange located on an opposite side of the transition relative to the intermediate section such that the flange extends from a part of the section of reduced diameter, the outward-extending circumferential flanges having a peripheral outer edge of a predetermined diameter that closely matches the outer diameter of the intermediate section.
 23. A watertube according to claim 22, wherein the transitions and outwardly-extending circumferential flanges are integral, formed parts of the watertube.
 24. A watertube according to claim 22, wherein the outwardly-extending circumferential flanges are provided by separately-manufactured end fittings that are welded to the end sections. 